The present invention relates to electromechanical printing devices for printers of the series-parallel type.
Series-parallel type printers are well known. Their printing head is reciprocated with a rectilinear motion parallel to the lines of printing and comprises n elements (n being a positive whole number) each able to print a succession of k consecutive dots along a line (k being a positive whole number). To provide movement of the printing head, present-day printers use a rotary motor coupled to an eccentric (or to a cam) placed in an aperture provided in the printing head. Furthermore, these printers comprise an auxiliary rotary motor coupled to a device for moving the printing sheet and a circuit for controlling the motors. This circuit controls the motors so as to reciprocate the printing head with a linear movement parallel to the lines of printing and so as to advance the printing sheet as soon as the printing of one line is finished. The two motors and their control circuit have the disadvantage of being expensive.
Furthermore, a printing device is known comprising a single motor, a roller supporting a sheet, a fixed printing head, first transmission means transforming the rotary movement supplied by the motor into a rotational movement of the roller about its axis, so as to cause said sheet to advance, second transmission means for transforming the rotary movement generated by said motor into a reciprocating rectilinear movement applied to the roller, parallel to its axis and synchronous with the movement of said sheet. Such a device is described in European patent application No. 80 400632.8, it has as drawback difficult access to the sheet, since the printing head is fixed to the frame, on the one hand and, on the other hand, the roller is connected to the frame by two mechanical transmission systems, one for providing its reciprocating rectilinear movement and the other for providing its rotation.